1. Field of the Invention
The present invention relates generally to planar crankshafts on internal combustion engines and, more specifically, to a balance system for a planar crankshaft on a V configuration internal combustion engine.
2. Description of the Related Art
It is known to use a "V" configuration for an internal combustion engine on automotive vehicles. A majority of V-8 configuration engines employ a "cruciform" or "90-degree" style crankshaft; that is, a crankshaft with four throws which are each offset by ninety degrees (90.degree.). This crankshaft configuration is preferred over other available choices for a V-8 because it allows for a fully balanced engine with proper counterweights on the crankshaft.
Three other crankshafts which can be employed in the V-8 configuration engine to achieve even firing are "180-degree" style crankshafts; that is, a crankshaft with throws that are offset by one hundred eighty degrees (180.degree.) instead of ninety degrees (90.degree.). This crankshaft configuration is called "planar" or "flat" since all of the journals and throws are co-planar. The planar crankshaft allows for even firing banks of cylinders, i.e., each bank of cylinders has a consistent 180 degree firing interval whereas a V-8 engine with a cruciform crankshaft does not. This provides improved consistency in the airflow which makes the engine run smoother and more efficiently. The cruciform crankshaft V-8 engine is the only commonly produced engine configuration which does not have even firing banks of cylinders.
Although the planar crankshaft has worked well in the V configuration engine, it suffers from the disadvantage of an inherent second order imbalance which consists of shaking forces and moments that cycle at twice the speed of the crankshaft.
One attempt to achieve total balance in a planar crankshaft V-8 configuration engine is disclosed in U.S. Pat. No. 4,936,238 to Randle. This patent discloses a balance system having dual counter-rotating balance shafts which act to cancel out the vibrations which are inherent to the V configuration engine. The patented balance system is mounted on a side of the V configuration engine.
One disadvantage of the above patented balance system is that space is needed on the side of the engine to mount the balance system which may not be available. Therefore, there is a need in the art to provide a balance system for a planar crankshaft on a V configuration engine which is compact and does not require space on the side of the engine.